JP3482743B2 - Shrink film composed of lactic acid-based polymer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shrink film for labels and packaging, and more specifically, it has excellent transparency, impact resistance and shrinkability at low temperature, and has biodegradability in a natural environment. The present invention relates to a shrink film having both functions.

[0002]

2. Description of the Related Art Plastics bring about great convenience and benefit to human social life due to their excellent physical and chemical properties, and a huge amount is used. However, on the other hand, the huge amount of plastic waste generated after use is
Due to its toughness and difficulty of deterioration, waste causes various global environmental problems such as shortage of landfill, obstruction of landscape, threat to marine life, and environmental pollution.

As one method for solving these problems, while retaining the same functionality as plastics, it undergoes hydrolysis or microbial decomposition in the natural environment to finally become harmless carbon dioxide gas and water. Research on biodegradable polymers has been actively carried out in various countries, and various polymers such as starch modified products, biocellulose, polyhydroxyalkanoates, and polylactic acid compositions have been developed so far. However, many of these are not suitable for stretching and a shrink wrapping film could not be prepared.

A biodegradable shrink film for a label is disclosed in Japanese Patent Laid-Open No. 5-212709, in which polylactic acid or a copolymer of lactic acid and hydroxycarboxylic acid is used as a raw material. . The shrink film for labels shown in this patent had excellent basic heat shrinkage properties and degradability in a natural environment, but the impact resistance during use of the product was still insufficient.

[0005]

Therefore, the problem to be solved by the present invention is to overcome the drawbacks of the conventional shrink film made of lactic acid type polymer such as impact resistance, and to have excellent transparency, gloss and low temperature shrinkability. Another object of the present invention is to provide a biodegradable shrink film and a manufacturing method thereof.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a structural unit obtained by dehydration condensation of lactic acid and a polyester structural unit obtained by dehydration condensation of dicarboxylic acid and diol and / or Alternatively, by using a lactic acid-based polymer having a weight average molecular weight of 1 to 700,000, which contains a polyether polyester structural unit obtained by dehydration-condensing a dicarboxylic acid and a polyether polyol, a 1% shrinkage initiation temperature is 35 to 80 ° C.,

It is possible to produce a shrink film of a lactic acid-based polymer in which the impact resistance of a film having a thickness of 20 μm or more in a film impact test is 6 kgf · cm or more and the maximum shrinkage in the stretching direction is 35 to 90%. Furthermore, they have found that the shrink film is a practical shrink film having excellent impact resistance, which has low-temperature shrinkability, high transparency, and high glossiness, and completed the present invention.

That is, the present invention comprises a dehydration-condensing structural unit of lactic acid, a polyester structural unit in which a dicarboxylic acid and a diol are dehydrated and condensed, and / or a polyether polyester structural unit in which a dicarboxylic acid and a polyether polyol are dehydrated and condensed. including, Ri consists lactic acid-based polymer having a weight average molecular weight from 1 to 700,000, a thickness of 10 to 120 [mu] m, 1% yield
Shrinkage onset temperature is 35 ~ 80 ℃, film imper
Impact strength in a test test of 6 kgf · cm or more, stretching method
Maximum shrinkage direction is push from links film is 35 to 90%.

The present invention further comprises a dehydration-condensing structural unit of lactic acid, a polyester structural unit in which a dicarboxylic acid and a diol are dehydrated and condensed, and / or a polyether polyester structural unit in which a dicarboxylic acid and a polyether polyol are dehydrated and condensed. and a structural unit of the molecular weight increasing agent, Ri consists lactic acid-based polymer having a weight average molecular weight from 1 to 700,000, the thickness
10 to 120 μm, 1% shrinkage start temperature is 35 to 80 ° C.,
The impact strength of the film in the film impact test is 6
kgf · cm or more, the maximum shrinkage in the stretching direction is 35 to 90
Is a push from link film is%.

Shrin composed of the lactic acid-based polymer of the present invention
Cheops Irumu an optical histological characteristics test method (JIS-K710
The haze value (haze value) in 5) is 0.1 to 20%.

More specifically, the shrink film made of the lactic acid-based polymer of the present invention is
It is characterized by containing 3 to 60% by weight of a lactic acid polymer of a polyester structural unit obtained by dehydration condensation of a dicarboxylic acid and a diol and / or a polyether polyester structural unit obtained by dehydration condensation of a dicarboxylic acid and a polyether polyol. is there.

[0012]

The present invention will be described in more detail below. The lactic acid-based polymer used in the present invention is a dehydration-condensed structural unit of lactic acid, a polyester structural unit in which a dicarboxylic acid and a diol are dehydrated and condensed, and / or a polyether polyester structural unit in which a dicarboxylic acid and a polyether polyol are dehydrated and condensed. It is a lactic acid-based polymer having a weight average molecular weight of 1 to 700,000 including

The lactic acid-based polymer is obtained by polymerizing an aromatic and / or aliphatic diol or polyether polyol with an aromatic and / or aliphatic dicarboxylic acid and lactic acid or a lactide which is a dimer of lactic acid, or It is obtained by copolymerizing an aromatic polyester and / or an aliphatic polyester or a polyether polyester composed of these components with lactic acid or lactide which is a dimer of lactic acid.

As the lactic acid component, L, D, DL-lactic acid,
Examples of the dicarboxylic acid component include those having a methylene chain length of 2 to 10, such as adipic acid, sebacic acid and succinic acid. The diol component has a main chain having 2 to 6 carbon atoms, for example, ethylene glycol, propylene glycol, butylene glycol, 1,4-butanediol,
Examples of 1,6-hexanediol and the like, and polyether polyols include polyethylene glycol, polypropylene glycol, polybutylene glycol and the like.

Of these, it is particularly preferable to use adipic acid and sebacic acid as the dicarboxylic acid component, propylene glycol as the diol component, and polypropylene glycol as the polyether polyol.
In order to have sufficient impact strength as a shrink film, the proportion of these polyester and / or polyether polyester components in the polymer is preferably about 3 to 60% by weight, and from the viewpoint of practicality, it is 5 to 40% by weight.
Is more preferable.

As a method for producing polylactic acid, a method of synthesizing lactide which is a cyclic dimer from lactic acid and obtaining a high molecular weight polylactic acid by ring-opening polymerization is often used. A method of synthesizing polylactic acid is also used. Further, the copolymer may be further polymerized by adding one or more auxiliary components such as aliphatic polyester, aromatic polyester, caprolactone, vinyl acetate, ethylene terephthalate polymer and ethylene vinyl alcohol during or immediately after polylactic acid polymerization. Is obtained by

The lactic acid used as a raw material is obtained by fermenting renewable resources such as sugar and starch. Also,
It can also be synthesized from petrochemical raw materials. The raw material lactic acid used for production may be any of optical isomers such as D isomer, L isomer, meso isomer, racemic isomer, or a mixture thereof. At that time, the ratio (L / D) of L body and D body is 100.
It can be used in all compositions from / 0 to 0/100.

The lactic acid-based polymer used in the present invention is
The lactic acid-based polymer can be made to have a higher molecular weight by adding a high-molecular weight agent, though it may be at any stage of the polymerization. The high molecular weight agent used in the present invention preferably has biodegradability itself, and examples thereof include a polyvalent carboxylic acid and / or its acid anhydride, or a polyvalent isocyanate. Examples of the polyvalent carboxylic acid include trimellitic acid and pyromellitic acid, and examples of the oxide anhydride include succinic anhydride, trimellitic anhydride, and pyromellitic anhydride.

As the polyvalent isocyanate, 2,4
-Tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate xylylene diisocyanate,
There are hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, triphenylmethane-4,4 ′, 4 ″ -triisocyanate and the like.

The amount of these high molecular weight agents added may be about 0.01 to 5% by weight based on the lactic acid-based polymer. By using these high molecular weight agents, the lactic acid-based polymer without the high molecular weight agent is added. The weight average molecular weight of a polymer, usually a lactic acid polymer having a weight average molecular weight of about 300,000, can be increased to about 600,000 to 700,000.

The weight average molecular weight of the lactic acid-based polymer used in the present invention is usually in the range of 10,000 to 700,000, among which 50,000 to 300,000 is preferred from the viewpoint of high strength and excellent moldability. More preferable. In addition to the lactic acid-based polymer, the shrink film of the present invention may contain other polymers or plasticizers, stabilizers, antioxidants, antiblocking agents, antifog agents, colorants, etc. as the second and third components as required. You may include an additive.

The polymer may include aliphatic polyester, polyvinyl alcohol, polyhydroxybutyrate-hydroxyvalerate, starch-based polymer and the like, and additives include polyester plasticizers such as 1,3 butanediol and adipic acid, and the like. Plasticizers such as dioctyl phthalate, polyethylene glycol adipic acid, epoxidized soybean oil, stabilizers such as carbodiimide,

Antioxidants such as 2,6-di-tert-butyl-4-methylphenol (BHT) and butyl hydroxyanisole (BHA), silica, antiblocking agents such as talc, glycerin fatty acid ester, An antifogging agent such as monostearyl citrate, a coloring agent such as titanium oxide, carbon black and ultramarine may be contained.

The film is produced by extrusion molding by the T die casting method, but the lactic acid type polymer has a high hygroscopic property and a strong hydrolyzing property, so that it is necessary to control the water content. In the case of extrusion molding using an extruder, it is necessary to form a film after dehumidifying and drying with a vacuum dryer or the like. In addition, film formation by a vent-type twin-screw extruder has a high dehydration effect, so that film formation can be performed efficiently.

It is also possible to carry out multi-layering by using a plurality of extruders. In this case, a polymer recovery product having inferior physical properties is put in the center layer and a virgin layer having excellent strength is used as both outer layers to improve the strength. It is also possible to reinforce. In addition, it is possible to prevent the colorant component from directly contacting foods, etc. by adding the colorant only to the central layer, and by including the functional additive only in both outer layers, it is possible to add a small amount of the effective effect. It is also possible to obtain

The melting temperature at the time of sheeting the lactic acid-based polymer is not particularly limited, but usually 10 to 10 from the melting point.
The temperature is 50 ° C. higher. The melt-extruded sheet is usually cast to a predetermined thickness and cooled if necessary. At that time, if the sheet thickness is thick, a touch roll and an air knife are used, and if it is thin, electrostatic pinning is used properly to obtain a uniform sheet. The distance between lips for melt extrusion is preferably 0.2 to 3.0 mm, and particularly preferably 0.2 to 1.5 mm in view of film forming properties.

As a stretching treatment method, a lactic acid-based polymer is melt extruded to form a sheet and subjected to a longitudinal stretching treatment, or after omitting this, simultaneous biaxial stretching or sequential biaxial stretching is performed. It is carried out during transverse stretching or transverse uniaxial stretching, but as a method for collecting the shrink film, a transverse stretching method using a tenter is preferable in terms of practicality because a wide product can be obtained.

The heating temperature during stretching is the glass transition temperature (T
g) to a temperature higher than Tg by 50 ° C., but from the viewpoint of the surface state of the sheet and the transparency, it is 10 to 4 from Tg.
A temperature range of 0 ° C. higher is especially preferred. Although the draw ratio varies depending on the purpose, it is usually 3 to 15 times, and more preferably 4 to 10 times in terms of surface magnification. The draw ratio in each direction of biaxial stretching is 2
-10 times, preferably 3 to 7 times, more preferably 4 to 6 times
Double.

In the case of uniaxial stretching, it is 3 to 7 times, more preferably 4 to 6 times, and 1.1 to 1.9 times, preferably 1 in order to suppress expansion in the non-stretching direction during shrinkage. .2-
You may give a weak stretch of 1.5 times. Immediately thereafter, Tg
By cooling below, a stretch-oriented film can be obtained. In the present invention, the glass transition temperature (Tg) and the melting point are T _ig and T _pm specified in JIS-K-7121, and the heating rate is 10 ° C / min.

The thickness of the produced film is not particularly limited, but is 10 to 30 from the viewpoint of impact resistance and excellent shrinkage characteristics such as shrinkage starting temperature and shrinkage orientation.
0 μm is preferable, and 20 to 120 μm in terms of practical use
Is more preferable.

When used as a heat-shrinkable packaging material or a material for a heat-shrinkable label, the shrink temperature of the shrink film of the present invention is a heating temperature from a glass transition temperature (Tg) to a temperature lower than the melting point (Tm). From the viewpoint of shrinkage arrival time, contents protection, energy cost, etc., 20 ° C from Tg
It is preferable to carry out at a temperature from a high temperature to 20 ° C. below the melting point (Tm).

From a practical point of view, in order to avoid the influence of the temperature of the contents, the shrinkage performance at low temperature is important.
00 ° C is more preferable. From this point, the 1% shrinkage initiation temperature of the shrink film of the present invention is preferably 35 to 80 ° C, but it is particularly preferably in the range of 45 to 80 ° C from the viewpoint of storage stability at room temperature. As for the shrinkage performance, the maximum shrinkage in the stretching direction is 35 to 90%, preferably 50 to 90.
%, More preferably 50 to 75%.

When the maximum shrinkage ratio is 35% or more, uniform shrink-wrapping can be performed without wrinkles or loosening phenomenon, and the practical shrinkage becomes good. On the other hand, when it is 90% or less, the stretched film can be stably formed. In addition,
In the present invention, the contraction start temperature is defined as the 1% contraction start temperature, which is the lowest temperature at which 1% contraction occurs when immersed for 60 seconds in a warm water bath heated to a predetermined temperature.

The maximum shrinkage ratio is that the shrink film of the present invention is heat-treated in a warm water bath at 100 ° C. for 60 seconds until the shrinkage of the film is almost in equilibrium, and heat-treated from the length (L1) of the original shrink film. The value obtained by subtracting the length (L2) of the obtained film divided by the length of the original film is expressed as a percentage (%). That is, the maximum shrinkage rate (%) = (L1−L2) / L1 × 100.

With regard to the physical and optical performance of the shrink film, it is preferable that the impact strength value is high in order to withstand external impacts during product manufacturing and product transportation.
In addition, the transparency of the film is important in order to make the contents of the packaged product look beautiful. As for impact resistance performance, impact resistance strength of 6 kgf cm or more is required, and preferably 6 to 5
It is 0 kgf cm, more preferably 7 to 50 kgf cm. As the transparency, a haze value is 0.1 to 20%, preferably 0.1 to 10%.

The impact strength value referred to in the present invention is JIS-P-8.
Measured by the film impact test method of 134. The transparency means that measured by the haze value (cloudiness value) of JIS-K-7105.

The shrink film obtained in the present invention is
It has excellent properties such as biodegradability, low-calorie burning properties, and no generation of harmful gases during combustion, which are the characteristics of lactic acid-based polymers, and at the same time has good transparency, gloss, impact resistance, and low-temperature shrinkage properties. In addition, it does not cause bleaching, shrink labels such as PET bottles, cap seals and spray cans, video tapes, beverage cans, toys, general packaging such as confectionery subdivisions, building materials, fibers, pallets. Suitable for industrial packaging such as.

[0039]

【Example】

(Preparation example of raw sheet, S1 to S5) Aliphatic polyester (weight average molecular weight: 21,000 (in terms of polystyrene), sebacic acid 50 mol%, propylene glycol 5
0 mol%) 7 parts by weight of L-lactide 87.5 parts by weight and D-lactide 2.5 parts by weight, the atmosphere is replaced with an inert gas, and the mixture is mixed at 165 ° C. for 1 hour to form an esterification catalyst. Then, 0.02 part of tin octanoate was added and the reaction was carried out for 8 hours. The obtained lactic acid-based polymer was a colorless transparent resin, and the weight average molecular weight was 2240, as determined by GPC, the glass transition temperature was 49 ° C, and the melting point was 156 ° C.

This raw material was dried to an extruding temperature of 180.
The sheet was extruded with an extruder (manufactured by Tanabe Plastic Co., Ltd.) having an L / D of 24 and an extrusion screw diameter of 50 mm under the condition of ° C to obtain a sheet having a thickness of 200 µm. Hereinafter, this sheet is referred to as S1.

Aliphatic polyester (weight average molecular weight:
310,000 (polystyrene conversion: 50 mol% sebacic acid, 50 mol% polypropylene glycol) 30 parts by weight of L-lactide 65 parts by weight and D-lactide 5 parts by weight were added, and the atmosphere was replaced with an inert gas. Then, the mixture was mixed at 180 ° C. for 1 hour, 0.02 part of tin octoate was added as an esterification catalyst, and the reaction was performed for 3 hours. The lactic acid-based polymer obtained is a colorless transparent resin and has a weight average molecular weight of GPC.
From the results of 1., the glass transition temperature was 55 ° C, and the melting point was 175 ° C.

This raw material was dried to an extruding temperature of 185
It was extruded by an extruder (manufactured by Tanabe Plastic Co., Ltd.) having L / D 24 and an extrusion screw diameter of 50 mm under the condition of ° C to obtain a sheet having a thickness of 200 µm. Hereinafter, this sheet is referred to as S2.

Polyester containing aromatic carboxylic acid and aliphatic dicarboxylic acid (weight average molecular weight of 47,000)
(Polystyrene equivalent), terephthalic acid 12 mol%, isophthalic acid 18 mol%, adipic acid 20 mol%, ethylene glycol 20 mol%, neopentyl glycol 30 mol%) L-lactide 65 parts and MESO-lactide 5 parts by weight Was added and the atmosphere was replaced with an inert gas, both were melted and mixed at 165 ° C. for 1 hour, and 0.02 part of tin octoate as an esterification catalyst was added and reacted for 6 hours. After the completion of the reaction, a lactic acid-based polymer having a weight average molecular weight of 125,000, a glass transition temperature of 52 ° C and a melting point of 162 ° C was obtained.

This raw material is dried to an extruding temperature of 180.
Extrusion was carried out under the condition of ° C using an extruder (manufactured by Tanabe Plastic Co., Ltd.) having an L / D of 24 and an extrusion screw diameter of 50 mm to obtain a sheet having a thickness of 200 µm. Hereinafter, this sheet is referred to as S3.

Aliphatic polyester (weight average molecular weight:
28,000 (polystyrene equivalent), 50 mol% succinic acid,
Ethylene glycol 50 mol%, glass transition point -3.5
C, melting point 105.0 ° C) 30 parts by weight of L-lactide 6
0 parts by weight and 10 parts by weight of D-lactide were added, the atmosphere was replaced with an inert gas, the mixture was mixed at 165 ° C. for 1 hour, and 0.02 parts of tin octoate was added as an esterification catalyst to obtain 7 parts by weight.
The reaction was carried out over time. The lactic acid-based polymer obtained was a slightly yellowish transparent resin and had a weight average molecular weight of 153,000 according to the GPC results, a glass transition temperature of 51 ° C. and a melting point of 165.
It was ℃.

This raw material is dried to an extruding temperature of 180.
Extrusion was carried out at a temperature of ° C using an extruder (manufactured by Tanabe Plastic Co., Ltd.) having an L / D of 24 and an extrusion screw diameter of 50 mm to obtain a sheet having a thickness of 200. Hereinafter, this sheet is referred to as S4.

L-lactide 93 parts, D-lactide 2
After adding 0.5 parts of pyromellitic dianhydride to 100 parts of lactide and 15 parts of toluene, and dissolving and mixing in a nitrogen gas atmosphere at 175 ° C. for 0.25 hours,
Add 0.03 part of tin octoate as a ring-opening polymerization catalyst, and add 3
Polymerization was carried out for a time.

Furthermore, a polyester containing an aromatic dicarboxylic acid component and an aliphatic dicarboxylic acid component (terephthalic acid component 14 mol%, isophthalic acid component 16 mol%, adipic acid component 20 mol%, ethylene glycol component 28 mol%, neopentyl Weight average molecular weight of 45,200 consisting of 22 mol% of glycol component, number average molecular weight of 24,70
5 parts of 0) was added and the reaction was carried out for 3 hours.

After the reaction, toluene was removed under reduced pressure. The lactic acid-based high molecular weight polyester produced has a weight average molecular weight of 51.
It was a colorless and transparent resin having a molecular weight of 7,000 and a number average molecular weight of 179,000. It had a glass transition point of about 56 ° C and a melting point of about 152 ° C. This raw material is dried in an absolutely dry condition, and the extrusion temperature is 180 ° C., L / D 24 and extrusion screw diameter 5
When it was extruded with a 0 mm extruder (manufactured by Tanabe Plastic Co., Ltd.), a sheet having a thickness of 200 μm was obtained. Hereinafter, this sheet is referred to as S5.

(Examples 1 to 8) Preparation of shrink film S1 to S5 were selected as original sheets, and shrink films were prepared at the stretching temperature and the stretching ratio shown in Table 1. As a result, these shrink films had excellent properties as shown in Table 2. As the physical property measuring method, was used.

Haze: JIS K7105  Impact strength: JIS P8134  Modulus: JIS K7127

1% shrinkage initiation temperature: The lowest temperature in the range of 30 to 100 ° C. at which 1% shrinkage occurs when the film is immersed in a heated hot water bath for 60 seconds. In addition, the shrinkage percentage is the percentage (%) obtained by dividing the shrinkage length by the original size when heat-treated in a hot water bath heated to 100 ° C.
It is represented by.

Maximum shrinkage: This is the shrinkage when heating is performed at 100 ° C. for 60 seconds until the shrinkage of the film almost reaches equilibrium. Practical Shrinkability: A glass bottle was covered with a film processed into a cylindrical shape with a margin of plus 5%, and the finished state when the bottle was covered with a shrink tunnel was visually observed. The setting condition of the shrink tunnel is 100
The finished state was evaluated as follows, at 5 ° C for 5 seconds.

◯: Occurrence of wrinkles and distortion was observed, and there was no problem in practical use as a product. Δ: Insufficient shrinkage remained in the small diameter part. X: What cannot be completely covered.

It was found that Examples 1 to 8 have practical properties such as sufficient transparency as a shrink film, impact resistance, and excellent low temperature shrinkability. In addition, they have high rigidity and excellent packaging suitability, and these shrink films were easily biodegraded by the compost test.

Comparative Example 1 Sheet S1 was stretched 1 × 2 times and the same test as in Example 1 was conducted. As a result, the impact resistance value was 6 or less.

Comparative Example 2 The sheet S2 was stretched 1 × 2 times and the same test as in Example 1 was conducted. There was no problem with the impact resistance value, but wrinkles were observed due to insufficient shrinkage.

(Comparative Example 3) According to JP-A-5-212709, a weight average molecular weight of 100,000, L-form / D-form = 95.
A 200 μm sheet of polylactic acid (hereinafter abbreviated as PLA) having a / 5, a Tg of 51 ° C., and a Tm of 161 ° C. was prepared and stretched 1 × 5 times at a temperature of 140 ° C., but a film could not be formed.

Comparative Example 4 PLA sheet similar to Comparative Example 3 (weight average molecular weight 100,000, L-form / D-form = 95/5, T
g: 51 ° C, Tm161 ° C) at sheet temperature 70 ° C 1 ×
The same test as in Example 1 was performed after stretching 4 times. As a result, the impact resistance value was as low as 6 or less, and the performance as a shrink film was not satisfied.

[0060]

[Table 1]

[0061]

[Table 2]

[0062]

[Table 3]

[0063]

INDUSTRIAL APPLICABILITY The present invention provides a biodegradable shrink film excellent in transparency, gloss and low temperature shrinkability, which overcomes the impact resistance, which is a drawback of the conventional shrink film made of lactic acid type polymer, and a method for producing the same. Can be provided.

Claims (4)

(57) [Claims] 1. A weight containing a dehydration-condensed structural unit of lactic acid, a polyester structural unit in which a dicarboxylic acid and a diol are dehydrated and condensed, and / or a polyether polyester structural unit in which a dicarboxylic acid and a polyether polyol are dehydrated and condensed. average molecular weight from 1 to 700,000 of Ri lactic acid-based polymer from <br/> formation, thickness 10 to 120 [mu] m, 1% shrinkage starting temperature 3
5 to 80 ℃, resistance to film impact test of film
Impact strength of 6 kgf · cm or more, maximum shrinkage in the stretching direction
Push from link film but is 35 to 90%. 2. A dehydrated condensation structural unit of lactic acid, a polyester structural unit dehydrated and condensed of dicarboxylic acid and diol, and / or a polyether polyester structural unit dehydrated and condensed of dicarboxylic acid and polyether polyol,
Weight average molecular weight 1 including the structural unit of the high molecular weight agent
Ri consists 700,000 lactic acid-based polymer, the thickness is 10 to 120
μm, 1% shrinkage start temperature is 35-80 ° C.
Impact strength in film impact test is 6kgf · cm
Above, Interview <br/> link Film maximum shrinkage in the stretching direction is 35 to 90%. 3. The lactic acid-based polymer comprises a polyester structural unit obtained by dehydration condensation of a dicarboxylic acid and a diol and / or a polyether polyester structural unit obtained by dehydration condensation of a dicarboxylic acid and a polyether polyol. % Content of claim 1 or
Is a shrink film comprising the lactic acid-based polymer described in 2 . 4. A method for testing optical properties of plastics (JI
The haze value (cloudiness value) in S-K7105) is 0.1.
It is 20%, The shrink film of Claim 1 or 2 characterized by the above-mentioned.